This invention relates to a shaft bearing system useful in any rotary machine, whether it is the shaft that is driven rotatively or the bearing system that is rotated while the shaft is held stationary. More specifically, the invention concerns a casing for porous self-aligning bushings intended for bearing applications.
A recognized requirement in the art is, with most applications, that each bushing should self-align with the rotation axis to compensate for imperfections of a larger or smaller extent in the angular relationship of the axis of the bore or hub seat, wherein the bushing is mounted, to the mating planes of the various parts of the machine incorporating such bushings.
It is known that such self-aligning feature mainly is achieved by holding the spherical bushing urged from one side against a corresponding conical surface formed in the hub, by means of springs, collars, washers, which are held in position by subsequent upsetting or other conventional fastening methods.
Rotation is known to create, in the very thin toroid resulting from the diameter differential--i.e. the clearance--between the shaft and bushing, a pressure which drives the lubricant out along the shaft at both ends of the bushing, to cause leakage and "drying" of the bushing.
It is known that in order to cause the bushing to recover and take in again by capillary action such lubricant, additional collars and washers have been used heretofore, but with unsatisfactory results where operation about a vertical axis is involved, which also brings into play the necessity of overcoming the force of gravity.
Small imbalances in the rotary portion, or minor distortions in the triangulation of the bushing bore or shaft surface, are known to reflect in the generation of vibrations and/or noise and/or beats in the machine operation, which disadvantages the rigid pressure mount described above and employed conventionally cannot help even to attenuate.
It is further known that those machines--indeed little accepted but having a promising future--which are designed to have their shaft stationary and the rotary portion born on self-aligning bushings rigidly attached thereto, i.e. arranged to rotate therewith, make use of lubricant-impregnated porous bushings problematic owing to the centrifugal action due to rotation acting on the lubricant mass to overcome the capillary action of the bushing, thereby the bushing loses the lubricant contained in it by centrifugation out of its porous outer peripheral surface.